Exploring number space by random digit generation

There is some evidence that human subjects preferentially select small numbers when asked to sample numbers from large intervals "at random”. A retrospective analysis of single digit frequencies in 16 independent experiments with the Mental Dice Task (generation of digits 1-6 during 1min) confirmed the occurrence of small-number biases (SNBs) in 488 healthy subjects. A subset of these experiments suggested a spatial nature of this bias in the sense of a "leftward” shift along the number line. First, individual SNBs were correlated with leftward deviations in a number line bisection task (but unrelated to the bisection of physical lines). Second, in 20 men, the magnitude of SNBs significantly correlated with leftward attentional biases in the judgment of chimeric faces. Finally, cognitive activation of the right hemisphere enhanced SNBs in 20 different men, while left hemisphere activation reduced them. Together, these findings provide support for a spatial component in random number generation. Specifically, they allow an interpretation of SNBs in terms of "pseudoneglect in number space.” We recommend the use of random digit generation for future explorations of spatial-attentional asymmetries in numerical processing and discuss methodological issues relevant to prospective design

Incarnation and animation: physical versus representational deficits of body integrity

Two apparently disparate phenomena of defective body integrity are reviewed. The first concerns dysmelia, characterized by the congenital absence or deformation of limbs, and the focus of the review is on phantom sensations of people with this kind of physical integrity disorder. The second phenomenon consists of non-psychotic individuals' desire to have a healthy limb amputated, which is interpreted as a mismatch between the physical integrity of a particular limb and its representation in multimodal cortical areas of the brain. We outlined commonalities and differences between the two conditions and note the absence, in both areas of research, of a unified theory that would account for the reported phenomenology. Phantom limbs in dysmelia and the desire for limb amputation most likely are the consequence of very early developmental dissociations between physical and phenomenal body shapes. They are mirror images of one another in that the former constitutes an "animation without incarnation” and, the latter, an "incarnation without animation

Mapping collective behavior--beware of looping

We discuss ambiguities of the two main dimensions of the map proposed by Bentley and colleagues that relate to the degree of self-reflection the observed agents have upon their behavior. This self-reflection is a variant of the "looping effect" which denotes that, in social research, the product of investigation influences the object of investigation. We outline how this can be understood as a dimension of "height" in the map of Bentley et a

When Digits Help Digits: Spatial–Numerical Associations Point to Finger Counting as Prime Example of Embodied Cognition

Spatial–numerical associations (SNAs) are prevalent yet their origin is poorly understood. We first consider the possible prime role of reading habits in shaping SNAs and list three observations that argue against a prominent influence of this role: (1) directional reading habits for numbers may conflict with those for non-numerical symbols, (2) short-term experimental manipulations can overrule the impact of decades of reading experience, (3) SNAs predate the acquisition of reading. As a promising alternative, we discuss behavioral, neuroscientific, and neuropsychological evidence in support of finger counting as the most likely initial determinant of SNAs. Implications of this “manumerical cognition” stance for the distinction between grounded, embodied, and situated cognition are discussed

Superstitiousness in obsessive-compulsive disorder

It has been speculated that superstitiousness and obsessivecompulsive disorder (OCD) exist along a continuum. The distinction between superstitious behavior italic>and superstitious belief, however, is crucial for any theoretical account of claimed associations between superstitiousness and OCD. By demonstrating that there is a dichotomy between behavior and belief, which is experimentally testable, we can differentiate superstitious behavior from superstitious belief, or magical ideation. Different brain circuits are responsible for these two forms of superstitiousness; thus, determining which type of superstition is prominent in the symptomatology of an individual patient may inform us about the primarily affected neurocognitive systems

Suppressing versus Releasing a Habit: Frequency-dependent Effects of Prefrontal Transcranial Magnetic Stimulation

When subjects are required to generate a random sequence of numbers they typically produce too many forward and backward ‘counts' (e.g. 5-6, 4-3). This counting bias is interpreted as the consequence of an interference by overlearned tendencies to arrange numbers according to their natural order. Inhibition of such well-learned routines is known to rely on frontal lobe functioning. We examined differential effects of slow (1 Hz) and fast (10 Hz) repetitive transcranial magnetic stimulation (rTMS) over the left or right dorsolateral prefrontal cortex (DLPFC) on random number generation (RNG) performance. Eighteen healthy men performed an RNG task. Those subjects stimulated over the left DLPFC showed a frequency-dependent rTMS effect: counting bias was significantly reduced after the 1 Hz stimulation compared with baseline, but significantly exaggerated after the 10 Hz stimulation compared with 1 Hz stimulation. In contrast, the sequences of the subjects stimulated over the right DLPFC showed the well-known excess of counting in all conditions (i.e. baseline, 1 Hz and 10 Hz). These findings confirm the functional importance of specifically the left DLPFC in sequential response production and show, for the first time, that rTMS affects cognitive processing in a frequency-dependent manne

Hand movement observation by individuals born without hands: phantom limb experience constrains visual limb perception

Increasing evidence suggests that the visual analysis of other people's actions depends upon the observer's own body representation or schema. This raises the question of how differences in observers' body structure and schema impact their perception of human movement. We investigated the visual experiences of two persons born without arms, one with and the other without phantom sensations. These participants, plus six normally-limbed control observers, viewed depictions of upper limb movement under conditions of apparent motion. Consistent with previous results (Shiffrar M, Freyd JJ (1990) Psychol Sci 1:257), normally-limbed observers perceived rate-dependent paths of apparent human movement. Specifically, biologically impossible motion trajectories were reported at rapid display rates while biologically possible trajectories were reported at slow display rates. The aplasic individual with phantom experiences showed the same perceptual pattern as control participants, while the aplasic individual without phantom sensations did not. These preliminary results suggest that phantom experiences may constrain the visual analysis of the human body. These results further suggest that it may be time to move beyond the question of whether aplasic phantoms exist and instead focus on the question of why some people with limb aplasia experience phantom sensations while others do not. In this light, the current results suggest that somesthetic representations are not sufficient to define body schema. Instead, neural systems matching action observation, action execution and motor imagery likely contribute to the definition of body schema in profound ways. Additional research with aplasic individuals, having and lacking phantom sensations, is needed to resolve this issu

Antibacterial Effects of Endodontic Dressings on Enterococcus Faecalis in Human Root Dentine

Svrha istraživanja bila je procijeniti antimikrobnu aktivnost kalcijeva hidroksida (Calasept) i klorheksidina (CHX-a) u različitim koncentracijama u odnosu prema bakteriji *Enterococcus *faecalis u dentinu ljudskog korijena u dubini do 100 μm. Materijal i metode: Do standardne veličine ( ISO 40 ) prošireno je 48 ljudskih korijenskih kanala te inokulirano 21 dan bakterijom *Enterococcus faecalis*. Nakon toga kanali su bili tretirani jednim od sljedećih preparata: 2-postotnim, 1-postotnim ili 0,2-postotnim klorheksidinskim gelom, gutaperkom koja otpušta CHX (aktivni štapić) i kalcijevim hidroksidom, a destilirana voda služila je kao kontrola. Na kraju jednotjednoga dezinfekcijskog razdoblja uzeti su uzorci dentina pomoću proširivača i H-pilice (ISO 45 i 50) te su nasađeni na ploče s Columbia agarom. Rast bakterija procjenjivao se brojenjem jedinica koje stvaraju kolonije (CFU-om; engl. colony forming units) i to nakon inkubacije od 24 i 48 sati. Rezultati: CHX gelovi penetrirali su u dentin čak do 100 μm. Dvopostotni CHX gel bio je malo jači od jednopostotnoga (p-vrijednost 0,0925)samo u uzorku perifernog dentina 48 sati nakon inkubacije, a 0,2 postotni je imao manji učinak na *E. faecalis* od 2-postotnoga (p-vrijednost 0,0191). U uzorku centralnog dentina nije bilo razlike u djelovanju CHX gelova. Općenito, CHX gelovi bili su učinkovitiji od drugih ispitivanih medikamenata. Nije bilo statistički veće razlike između Ca(OH)2 i destilirane vode. Zaključak: Za djelotvornu eliminaciju E. faecalis, posebice u dubljim slojevima dentina, potrebno je koristiti se CHX-om u koncentraciji od 1 posto i većoj. Između posjeta pacijenata liječniku, intrakanalni uložak 2-postotnoga CHX gela mogao bi uništiti E. faecalis in vivo.The aim of this in vitro study was to assess antimicrobial activity of calcium hydroxide (Calasept) and chlorhexidine (CHX) in various concentrations with respect to Enterococcus faecalis in human root dentine up to 100 μm. Material and Methods: Forty-eight human root canals were enlarged to standard size (ISO 40) and inoculated with Enterococcus faecalis for 21 days. After inoculation the canals were medicated with one of the following: 2 %, 1 % and 0.2 % chlorhexidin gel, Chlorhexidine releasing gutta-percha points (active point), calcium hydroxide and aqua distillate (aqua dest.). Aqua dest. served as control medium. At the end of a disinfection period of one week dentine samples were collected with reamer and H-file (ISO 45 and 50) and put onto Columbia agar plates. Results: Bacterial growth was assessed by counting the colony forming units (CFU) after 24 hours and 48 hours of incubation. CHX gels could penetrate dentine up to 100 μm. Two % CHX gel is slightly stronger than 1 % CHX gel (p-value 0.0925) only in the peripheral dentine sample after 48 hours of incubation, and 0.2 % CHX gel had less effects on E. faecalis than 2 % CHX (p-value 0.0191). In the central dentine sample no difference between the CHX gels could be observed. In general, CHX gels were more effective than the other medicaments tested. No significant difference between Ca(OH)2 and Aqua dest. could be observed. Conclusion: For effective elimination of E. faecalis, especially in deeper dentine-layers, CHX concentrations of at least 1 % are necessary. An intracanal, interappointment dressing of 2 % CHX may have the potential to eliminate E. faecalis in vivo